One of the country's largest insurance companies says it needs to tweak some of its property and casualty insurance plans, after announcing it will book about $257 million in expenses stemming from recent catastrophes.

On Monday, Intact Financial Corp. said the costs are related to the flooding in Alberta and Toronto and the deadly Lac-Megantic train derailment in Quebec.

"The devastation brought on by recent flooding and torrential rain is unprecedented," said Charles Brindamour, Intact's chief executive officer, in a statement.

"The scope of the damage and destruction that we have witnessed in recent weeks is a stark reminder that we must adapt the protection offered to Canadians to ensure it remains sustainable in light of the greater prevalence and severity of weather events."

Glenn McGillivray, managing director of the Institute for Catastrophic Loss Reduction, said increasingly dense cities, crumbling infrastructure and the changing climate are likely to increase weather-related losses over the coming years.

"We're building more and more and putting more and more into our cities, so when you get something like a heavy rainstorm — it's going to hurt a little bit more," he said.

Jeff Fenwick, an analyst at Cormark Securities Inc., said Intact has been focused recently on repricing home insurance products and providing more specifics around what's covered and what isn't.

"About 20 years ago, there weren't nearly as many people who had finished their basement and put expensive audio visual equipment, and that type of thing, down there," Fenwick said.

"So now the magnitude of the losses when your basement floods tends to be quite a bit larger."

That means insurance costs are likely to go up for Canadians, as severe weather events become increasingly prevalent, said Fenwick.

"We'll probably start to see some rising costs as well if these things continue to become more common over time," he said.

Toronto-based Intact estimates it will record about $123 million or 92 cents per share in after-tax catastrophe losses in its second quarter.

That will be mainly due to about $300 million of costs for Intact customers in Alberta following storms and flooding that swept through several communities.

The financial blow to Intact will be softened by reinsurance — essentially insurance for insurance companies.

The Alberta disaster, alone, will result in $105 million or 79 cents per share net of reinsurance in the second quarter ended June 30.

In the third quarter, which began July 1, Intact estimates it will record an additional $134 million, or $1.01 per share, in after-tax catastrophe losses.

That will include a $25 million cost associated with the Lac-Mégantic train derailment that killed an estimated 47 people and devastated the small Quebec town.

The severe rain storm that impacted thousands of Intact customers in the Greater Toronto Area in early July resulted in an estimated $170 million of insurable damages, the company said.

It's unclear if the losses will surmount the $1 billion the industry booked after the fires in Slave Lake, Alta., in 2011, or the $500 million of insured losses that Intact recorded following the 2005 Ontario ice storms, said Fenwick.

"This will certainly be one of the more sizable years for catastrophe losses for insurance firms," he said.